# I am studying a thermal convection problem and I have a question about it

kkanade
Forum Coordinator

I am studying a thermal convection problem and I want to identify whether I have natural or forced convection. How can I do it?

kkanade
Forum Coordinator

## Comments

Ri<<1you have forced convection, while ifRi>>1you have natural convection. ForRi≈1it is mixed convection.You can calculate it as

Ri = Gr/Re^2where

Gr is the Grashof number

Re is the Reynolds number

or as Ri = [beta*g*(T_s - T_ref)*L]/V^2

where

g is the gravitational acceleration

beta is the thermal expansion coefficient

T_s is the (hot) surface temperature

T_ref is the reference temperature

L is the characteristic length

V is the velocity